1. Field of the Invention
The present invention relates to the covering of a wound, lesion or the like on an animal body with an adherent, skin-like collagen membrane to effect protection therefor during the healing process. The invention also relates to an iontophoretic process whereby collagen fibrils are electrochemically-linked with each other and to the wound or lesion site to provide such membranes.
2. Description of the Prior Art
The need to provide protection for a wound, lesion or the like on an animal body during the healing thereof has long been recognized. This need is predicated upon many factors, not the least of which are the requisites of precluding infectious or other foreign material from entering the open wound as well as the desirability of alleviating pain and loss of body fluids attendant such open areas on the body.
Various techniques have been devised in the past to achieve some amount of protection for open wounds, burns, etc. by means of bandaging or application of some physical barrier intimate the open wound. However, mere physical barriers have proved inadequate in many respects, the most notable deficiency including the inability of these bandage-like protective coatings to retain fluids while permitting oxygen permeability therethrough. Accordingly, the ability to curtail drainage of bodily fluids which accumulate in the wound as well as the ability to maintain oxygen permeability are foreclosed. In an effort to obviate these deficiencies, various surgical grafting techniques have been developed.
Probably the most widely accepted and employed of these grafting procedures involves the application of skin to the area of interest. Fundamentally, these skin graftings are capable of providing enhanced permeability due to their inherent characteristics and thus minimize the masking effects of such physical barriers as bandages. As a norm, the skin employed for such grafts may be provided by a donor or may be removed from the patient to be treated himself. It has been shown, however, that the use of donated skin provides concomitant problems of, particularly, rejection. Such rejection, which results from the introduction of material foreign to the recipient's body, manifests a lack of adherence and accompanying sloughing off of grafted area. Accordingly, to avert this rejection phenomena, the most successful grafting may be achieved by employing skin sections removed from the patient to be treated. However, under many circumstances this is also highly undesirable.
In an effort to provide a viable alternative to skin grafting to effect protection for open wounds, lesions and the like on an animal body, investigation into the adherence of other naturally occurring materials to the area of interest has witnessed wide-spread attention. It has been determined that collagen may admirably be employed to achieve these ends. Collagen is a proteinaceous fiber existing as a fundamental constituent of connective tissue, cartilage and bone in all mammalians. Collagen possesses numerous inherent characteristics which render it readily adaptable for use as a protective film or membrane for a wound, etc., such characteristics comprising, inter alia, flexibility, substantial insolubility in water and body fluids, permeability to these fluids as well as permeability to oxygen and many commonly used topical antibiotics. Another characteristic of collagen rendering it highly suitable for such application is its ability to electrochemically-link between and among fibrils to effect a membranous film.
In recognition of the highly favorable, inherent characteristics of collagen which render it adaptable for providing protective films for wounds, lesions and the like, I have developed a process for the formation of adherent films disclosed in my U.S. Pat. No. 3,563,228 issued Feb. 16, 1971, incorporated herein by reference. Briefly described, that earlier patent relates to the application of an electric field, of suitable polarity, to a dispersion of undenatured collagen fibrils to cause electrochemical-linking between the fibrils of the dispersion. The collagen, thus applied, is also capable of linking to native collagen fibrils exposed at the wound site to effect a highly adherent, protective surface thereover.
The essence of the ability of collagen to form such protective surfaces rests in large part with the physical and chemical characteristics of the fibrils in the dispersion. The preparation of collagen fibrils to form such a dispersion, which may subsequently be used to form electrochemically-linked collagen membranes, involves a process of cutting, chopping, beating and otherwise damaging some portion of the fibrils, thus though to expose polar sites. The number of polar sites exposed along the length of the fibril will vary depending upon preparatory treatment, with some fibrils having polar sites uncovered entirely along the length thereof. The fibrils in the dispersion do not have the opportunity to contact and join each other by mating polarities. However, the statistical distribution yields sufficient opposing polarities located sufficiently close to each other that an additional electrical impetus electrochemically-links the fibrils together. Once linked, the collagen membrane exhibits substantial physical strength and is no longer soluble in the fluid of the initial dispersion.
Microscopic examination reveals a substantial degree of both mechanical interlocking and joining between the fibrils of the collagen membrane and those exposed at the wound site. Accordingly, such films are extremely adherent to a wound and provide a great degree of protection therefor. As such films are semipermeable to bodily fluids, no undue accumulation thereof is exhibited. Similarly, as the membranes are oxygen permeable, prompt healing of the wound is enhanced.
In recognizing the advance over the prior art provided by my U.S. Pat. No. 3,563,228, it would be desirable to provide these adherent, skin-like protective coatings but without the need for application of an external power source to provide the iontophoretic impetus therefor, it being appreciated that the electric apparatus are often bulky and, ofttimes, require the patient to be treated at some central location. Accordingly, it is desirable to be able to provide these protective coatings by continuous treatment of the patient without significant restrictions upon ambulation or the necessity of confinement.